President Donald Trump unveiled new travel restrictions on visitors from eight countries — a replacement of a controversial travel ban that expired on Sunday.

Under the new rules that go into effect on October 18, people from Chad, Iran, Libya, North Korea, Somalia, Syria, Venezuela and Yemen will undergo extreme vetting, though the rules change depending on the nation in question. Syrians, for example, are completely barred for an indefinite period, while the restrictions on Venezuelan visitors apply only to senior government officials and their immediate families, according to the Associated Press.

Trump hailed his new policy in a statement Sunday: "As President, I must act to protect the security and interests of the United States and its people."

He also added in a tweet, "Making America Safe is my number one priority. We will not admit those into our country we cannot safely vet."

The new restrictions are the third incarnation of Trump’s travel ban. According to AP, the eight countries did not comply with new U.S. requirements that countries share information about travelers’ past criminal history or terror activity. The Department of Homeland Security said it also requires countries to issue electronic passports with biometric information. All nations of the world had 50 days to comply with the new requirements.

“These restrictions are necessary and conditions-based, not time-based,” a senior administration official told The Washington Post. "Those governments are simply not compliant with our basic security requirements."

The new restrictions do allow for some exceptions on a case-by-case basis. Valid visas are not going to be revoked under the new ban, officials said.

The new restrictions replace the expired travel ban that barred residents of Iran, Libya, Somalia, Sudan, Syria and Yemen. The original travel ban, which barred most visitors from seven majority-Muslim nations, will be heard by the Supreme Court this fall.

Some administration officials still maintain the legality of the blanket ban on refugees and visitors from those nations.

“The restrictions either previously or now were never, ever ever based on race, religion or creed," said the official in the Washington Post story.

Opponents have argued that the president does not have the authority to bar visitors by race, ethnicity or religious belief.

Senator Bob Menendez said he was "disappointed, but not surprised, that the Trump administration has failed once again to prioritize our long-term national security interests or stand up for human rights."